Field of the Invention
This invention relates to a lifting mast of a lifting frame of an industrial truck, in which the lifting frame is provided with load handling means that can be raised and lowered and the lifting mast has two vertical rails at a lateral distance from one another that are connected to one another by at least one cross member.
Description of Related Art
Lifting masts of this type are used in lifting frames of industrial trucks such as counterbalanced forklift trucks. Lifting masts of the prior art can be in the form of a stationary mast of a single-section lifting frame (also called a simplex lifting frame) or a telescoping mast of a multi-section lifting frame, such as a duplex lifting frame, which includes one stationary mast and one telescoping mast, or a triplex lifting frame, which includes a stationary mast and two telescoping masts.
On lifting masts of this type, the two vertical rails located at a lateral distance from each other are generally connected to one another by means of at least two cross members. The area between the two vertical rails then forms an area in which the operator located in a driver's position of the industrial truck can see through the load mast to the load handling means that can be raised and lowered on the vertical rails of the lifting mast.
Types of lifting masts are known in which the two vertical rails located at a lateral distance from one another on the lifting mast are connected to one another by means of at least three cross members. A first cross member is in the form of a bottom cross member that is located in the bottom area of the vertical rails. An additional cross member is in the form of a top cross member that is located in the upper area of the vertical rails. At least one additional cross member is in the form of a middle cross member that is located between the bottom cross member and the top cross member in the vertical direction of the lifting mast. When the lifting mast is in the form of a telescoping mast that can be raised and lowered as a multi-section lifting frame, the middle cross member, which is also raised and lowered depending on the lift position of the telescoping mast and, therefore, at different lift heights of a load handling means of the lifting mast, interferes with the ability of the operator located in the driver's position of the industrial truck to see the load handling means.
On lifting masts of the prior art, the cross member is a solid component, for example a steel plate. However, a solid component of this type presents a major obstacle to the ability of the operator operating the industrial truck to see the load handling means.
To reduce the obstacles to the ability of the operator operating the industrial truck to see the load handling means, it is already known that see-through openings can be created in the cross member that are in the form of solid components, such as an essentially rectangular steel plate, for example, in locations that are not subjected to major loads. A lifting mast with a solid cross member that is provided with see-through openings of this type is described, for example, in WO 2014/124932 A1. Even with a cross member that is provided with see-through openings of this type, at different lifting heights of a load handling means of the lifting mast, there is still interference with the ability of the operator operating the industrial truck to see the load handling means at various lift heights because the load handling means are hidden by the cross member. The operator must therefore move his or her head and/or upper body (torso) into awkward and uncomfortable positions to be able to see around the cross member or below the cross member to get a view of the load handling means.